Thyristor Short-Circuit Control for Drive System Overvoltage
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Solution Overview
Problem
Existing drive systems for battery-powered vehicles experience unintended braking torque and overvoltage issues due to faults in the self-commutated converter or its control and regulation device, particularly in field weakening mode, leading to unexpected braking and potential vehicle damage or injury.
Innovation Solution
A drive system utilizing three thyristors instead of contactors for controlled short-circuiting of stator-side connections, allowing for timed cancellation of the armature short-circuit and incorporating a star-connected thyristor pair configuration with a shunt resistor for functional testing, ensuring the device can be operational and minimize braking torque in case of faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a self-commutated converter is used in the drive system, then the vehicle can operate in field weakening mode for high-speed operation, but faults in the converter or control device cause unintended braking torque and overvoltage issues
Solution Approach 1:
The patent applies preliminary anti-action by providing a protective device that preemptively counteracts the harmful effects of converter faults. The device includes circuitry that detects fault conditions and automatically activates an alternative braking mechanism (resistor-based or mechanical) before the fault can cause unintended braking torque or overvoltage damage, thus preventing the harmful effects rather than merely responding to them
Solution Approach 2:
The patent implements beforehand cushioning by incorporating protective circuitry and alternative braking pathways that are prepared in advance to absorb and mitigate the impact of converter failures. The system includes energy dissipation paths and fault detection mechanisms that are ready to activate, cushioning the system against the sudden harmful effects of converter or control device faults
2Device complexity
If contactors are used for short-circuiting stator connections, then the device can be simple in structure, but it cannot be deactivated again and causes sudden vehicle stops
Solution Approach 1:
The patent replaces the mechanical contactor system with an electronic control system using semiconductor switches (IGBTs or MOSFETs) in an alternative braking circuit. This substitution allows for precise electronic control of the braking action, enabling the system to be activated and deactivated as needed, thereby eliminating the inability to control braking that plagues mechanical contactor systems while maintaining structural simplicity through integration
Solution Approach 2:
The patent applies dynamics by transitioning from a static, irreversible contactor-based short-circuiting mechanism to a dynamic, controllable electronic braking system. The alternative braking circuit with semiconductor switches can be dynamically activated and deactivated based on system conditions, allowing the braking torque to be controlled and canceled when no longer needed, thus enabling adaptive braking control
3Ease of operation
If thyristors are used for controlled short-circuiting, then the device can be deactivated, but functional testing during operation becomes difficult
Solution Approach 1:
The patent applies self-service by incorporating self-test functionality into the alternative braking circuit. The control device automatically performs functional tests of the thyristor-based short-circuiting mechanism during normal operation, using the existing control and measurement infrastructure to verify the braking circuit's readiness without requiring external testing equipment or system shutdown
Solution Approach 2:
The patent implements feedback by integrating measurement circuits that continuously monitor the state and functionality of the alternative braking circuit. The control device receives feedback signals from sensors and circuit diagnostics, allowing it to detect faults in the thyristor-based short-circuiting mechanism and activate appropriate protective measures or alert the operator to maintenance needs
4Device complexity
If no protective device is provided, then the system is simple, but faults cause overvoltage that can destroy the converter or other connected devices
Solution Approach 1:
The patent applies the intermediary principle by introducing a protective device that acts as a mediator between the self-commutated converter and the rest of the system. This protective circuit includes voltage clamping elements, surge protectors, or controlled switching pathways that intercept and manage overvoltage conditions before they can propagate to and damage the converter or other connected devices, thus shielding the system from harmful voltage spikes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables controlled and safe management of braking torque, preventing sudden vehicle stops and minimizing damage by allowing for timely cancellation of the armature short-circuit and ensuring the device's functionality during operation, thus enhancing safety and reliability.
Implementation Method 1
A drive system utilizes three thyristors instead of contactors for controlled short-circuiting of stator-side connections
Implementation Method 2
incorporating a star-connected thyristor pair configuration with a shunt resistor for functional testing
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The drive system has a permanent magnet synchronous machine (10) whose the stator-side ports (U,V,W) are electrically connected with alternating current (AC)-side terminals (R,S,T) of a self-commutated converter (8) respectively. Three thyristors (44) of a short circuit controlling device (26) are electrically connected in delta connection and are electrically connected with the stator-side port of the permanent magnet synchronous machine.